Multiple stimuli-responsive dual-emission material with locked diverse conformations for multimodal anti-counterfeiting and single-molecule white electroluminescence

The demand for dual-emission organic luminophores with multiple stimuli-responsiveness is rapidly increasing across various fields. However, their design and fabrication still face significant challenges, as these properties typically rely on specific molecular conformations and packing modes. In this work, we report two dual-emission molecules, 6-PTZ-FQ and 7-PTZ-FQ. 6-PTZ-FQ demonstrates fluorescence-thermally activated delayed fluorescence (TADF) dual-emission characteristics in both crystalline and low-concentration amorphous systems, due to the stable coexistence of its two conformational isomers. Owing to the temperature sensitivity of TADF, the crystal of 6-PTZ-FQ exhibits emission color modulation from green (526 nm) to yellow (551 nm) within the temperature range of −30 °C to 60 °C. Additionally, when its crystals are mechanically ground into a powder, it demonstrates high-contrast, reversible mechanochromic luminescence (MCL) behavior, with the emission wavelength shifting from 531 nm to 608 nm. The unique multi-stimulus-responsive behavior of 6-PTZ-FQ endows the material with unparalleled optical information encoding capabilities, demonstrating great potential for high-security anti-counterfeiting applications. Furthermore, both 6-PTZ-FQ and 7-PTZ-FQ exhibit dual-emission behavior in low-concentration amorphous systems, enabling highly efficient single-molecule warm white emission, with a maximum external quantum efficiency (EQE) of 10.2 %. This efficiency ranks among the highest reported for purely organic single-molecule warm-white OLEDs (CIEy < 0.41).